The existence of a dedicated Chemistry Core has a number of benefits to each research project, particularly where development and optimization of chemical techniques is not the primary research focus. As a whole, the Core also provides many functions that are equally important to each Project (e.g. syntheses, radioisotope handling, consultation, robotic equipment, training) but can provide it much more efficiently than each Project by itself. Centralization of personnel, resources and supplies will help to reduce the cost of the proposed research and result in a more efficient operation. Another important function of the Core is to provide compounds for research that have been 1) rigorously tested and conform the standards, are synthesized under identical, reproducible conditions in technically adequate ways, 2) analyzed according to a standard protocol prior to use, and 3) synthesized in sufficient amounts so that they are available to all Project researchers. Finally, the Core will also conduct its own research, as it has in the past, to further improve synthesis and design of chelates, reporters, dyes and drug carriers. This is possible by the experienced staff members of this Core and their expertise in different areas of chemistry including bioconjugation, chelate design, peptide synthesis, organic synthesis, protein chemistry and isolation, magnetic particle synthesis and analytical chemistry. The Core Directors have a proven track record of active productive collaborations with investigators across multiple institutions, particularly the Pi's of this P50. The attendance of the key core personnel in our inter-group meetings insures that the PSO's imaging needs are met and that cutting-edge technologies are appropriately exploited in a timely and accurate manner.